1. Field of the Invention
The present invention relates to a composite sensor and an acceleration sensor arranged to detect angular velocity and acceleration, for example.
2. Description of the Related Art
A composite sensor to detect angular velocity and acceleration by using a vibrator is known (e.g., see Japanese Unexamined Patent Application Publication No. 2006-105698 and Japanese Unexamined Patent Application Publication No. 2004-163376). Such a composite sensor includes a vibrator supported by a supporting beam such that the vibrator can be displaced in two axial directions that are substantially perpendicular to each other (e.g., X-axis direction and Y-axis direction) and a displacement detector to detect displacement in the Y-axis direction in a state in which the vibrator vibrates in the X-axis direction. When angular velocity acts on the composite sensor, a Coriolis force generated by the angular velocity acts in the Y-axis direction on the vibrator vibrating in the X-axis direction. This Coriolis force is generated at the same frequency as the vibration frequency of the vibrator, and thus, the composite sensor performs synchronous detection on a detection signal detected by the displacement detector at the vibration frequency so as to detect angular velocity. On the other hand, when acceleration acts on the composite sensor, the vibrator is displaced in the Y-axis direction, for example, due to the acceleration. Accordingly, the composite sensor detects displacement of the vibrator using the displacement detector so as to detect acceleration.
In the known composite sensor, both angular velocity and acceleration are detected using a common vibrator. Therefore, if the vibrator and the supporting beam are designed to detect angular velocity, the rigidity of the supporting beam is excessively high to accurately detect acceleration. As a result, the displacement of the vibrator caused by acceleration cannot be sufficiently ensured, and detection sensitivity for acceleration disadvantageously decreases. On the other hand, if the vibrator and the supporting beam are designed to detect acceleration, the rigidity of the supporting beam is excessively low. As a result, an acceleration detection signal is mixed with an angular velocity detection signal, such that detection accuracy for angular velocity disadvantageously degrades.